Rainwater Samples Research Articles

Methodology for Preconcentration and Determination of Silver in Aqueous Samples using Cloud Point Extraction

For the selective extraction of silver, a cloud point extraction (CPE) procedure was developed. After synthesizing the solvation species through the reaction of silver ions with 2, 4-dimethyl pentane-3-one (2,4 DMP), the salting-out agent (0.4 mol L-1 NaNO3) was added at 35 °C and, after 10 min, Triton X-114 was used to separate silver ions from aqueous solution. The type and quantity of salting-out agent, silver ion, temperature, heating time, and surfactant volume were all examined as important factors determining the CPE. The analytical curve in the 0.1-100 μg L-1 Ag range was straight at optimal conditions. The detection limit (LOD), quantification limit (LOQ), and enrichment factor (E) were 0.05 µg L-1, 0.15 µg L-1, and 200, respectively. The relative standard deviation (RSD) was estimated as 0.2-3.9% (n = 5) in relation to 1, 40, and 80 μg L-1 Ag. Flame atomic absorption spectrometry and spectrophotometry exploiting dithizone were used to assess the CPE accuracy. The proposed approach was then applied to river water, rain water and sand samples.

Spatiotemporal Variation of Hydrogen and Oxygen Stable Isotopes in the Yarlung Tsangpo River Basin, Southern Tibetan Plateau

Characterization of spatiotemporal variation of the stable isotopes δ18O and δD in surface water is essential to trace the water cycle, indicate moisture sources, and reconstruct paleoaltimetry. In this study, river water, rainwater, and groundwater samples were collected in the Yarlung Tsangpo River (YTR) Basin before (BM) and after the monsoon precipitation (AM) to investigate the δ18O and δD spatiotemporal variation of natural water. Most of the river waters are distributed along GMWL and the line of d-excess = 10‰, indicating that they are mainly originated from precipitation. Temporally, the δ18O and δD of river water are higher in BM series (SWL: δD = 10.26δ18O+43.01, R2 = 0.98) than AM series (SWL: δD = 9.10δ18O + 26.73, R2 = 0.82). Spatially, the isotopic compositions of tributaries increase gradually from west to east (BM: δ18O = 0.65Lon (°)-73.89, R2 = 0.79; AM: δ18O = 0.45Lon (°)-57.81, R2 = 0.70) and from high altitude to low (BM: δ18O = −0.0025Alt(m)-73.89, R2 = 0.66; AM: δ18O = −0.0018Alt(m)-10.57, R2 = 0.58), which conforms to the “continent effect” and “altitude effect” of precipitation. In the lower reaches of the mainstream, rainwater is the main source, so the variations of δ18O and δD are normally elevated with the flow direction. Anomalously, in the middle reaches, the δ18Omainstream and δDmainstream values firstly increase and then decrease. From the Saga to Lhaze section, the higher positive values of δ18Omainstream are mainly caused by groundwater afflux, which has high δ18O and low d-excess values. The δ18Omainstream decrease from the Lhaze to Qushui section is attributed to the combined action of the import of depleted 18O and D groundwater and tributaries. Therefore, because of the recharge of groundwater with markedly different δ18O and δD values, the mainstream no longer simply inherits the isotopic composition from precipitation. These results suggest that in the YTR Basin, if the δ18O value of surface water is used to trace moisture sources or reconstruct the paleoaltimetry, it is necessary to rule out the influence from groundwater.

Good Practices of Quality Control in the Area Surrounding of Natural Mineral Water Abstraction of São Pedro Do Sul Medical Spa (Portugal)

São Pedro do Sul medical spa is a space with a millenary tradition in providing health services from the natural hot groundwater. The main source of supply of this thermal unit, was along the time, the Traditional Spring, which in the last decades has been controlled, and shows to have constancy in the flow rate, with about 10 L/s, with a temperature of 68.6°C in the origin. From 1999 onwards, with the construction of new abstraction, Well AC1, with 500m deep, with a maximum flow rate of 12.2 L/s, at 67°C, the exploitation potential of this resource increased. Due to the fabulous characteristics of the resource’s potential (hot natural mineral water), there has been over time a great development in the spa medical activity, having already frequented these spa 25450 users per year, reflecting a maximum annual turnover of 5.4 million euros, coming from thermalism alone. Currently, there are two Bathhouses in operation and the resource is used, not only for therapeutic and wellness thermalism but also for geothermal uses and yet in the cosmetic area. This situation becomes the perfect scenario for attracting investment, increasing the circulation of people and goods, but also in the interest of building new bathhouses, hotels and restaurants and subsequently new roads, gardens, public drinking water and sanitation networks. All this pressure causes a lot of potential damage to the environment, including the underground water environment, and could eventually lead to the closure of the medical spa, if the natural mineral water from the abstractions become contaminated. In Portugal, there are several legally imposed defensive mechanisms of the mineral aquifer system, namely the implementation of the Protection Perimeter, but also the analytical control of the natural mineral water, at the abstraction head, both in chemical and microbiological terms, in addition to the orientation to have an automatic, on-line, record system associated to the abstractions, monitoring parameters such as: water level, flow rate, temperature, pH and conductivity of the water captured. However, the Sao Pedro do Sul medical spa go further, implementing an external monitoring system, consisting of: i) double piezometers (to sample groundwater at different depths), ii) street rainwater samplers, and iii) records precipitation and respective quality. Thus, in this paper, after a brief presentation of the importance of the resource and the physical aspects of the place (geology, hydrogeology and quality of the resource), the fundamental elements of the implemented external monitoring system and its main results are presented, showing that precipitation itself is already contaminated, that street rainwater sample presents chemical elements that are highly harmful to public health, and that groundwater sometimes presents very worrying results. Finally, some actions are mentioned that have been implemented to minimize the potential for contamination of natural mineral water from abstractions and the mineral aquifer system.

Different characteristics of microbial diversity and special functional microbes in rainwater and topsoil before and after 2019 new coronavirus epidemic in Inner Mongolia Grassland

Grassland ecosystems are vital terrestrial ecosystems. As areas sensitive to climate change, they are critical for assessing the effects of global climate change. In China, grasslands account for over 40% of the land area. There is currently limited information on microbial diversity evolution in different grassland areas, particularly microorganisms with ice nucleation activity (INA) and their potential resources with potential influence to regulate regional precipitation and climate. We used Illumina MiSeq to sequence the 16S rRNA V3–V4 hypervariable region and performed a simple droplet freezing experiment to determine the variation in the grassland microbial community species composition and community structure. Rainwater and topsoil samples from the Hulunbuir Grassland in Inner Mongolia collected over three years were characterized. The dominant bacterial genus in the rainwater was Massilia, and the dominant fungus was Cladosporium. Additionally, the dominant bacteria in the soil were Sphingomonas, and the dominant fungus was Gibberella. There were differences in the microbial communities before and after the coronavirus disease epidemic. Pathogenic microorganisms exhibited inconsistent responses to environmental changes. The low relative abundance of known high-INA microorganisms and the higher freezing temperature indicated that unknown high-efficiency biological ice nucleating particles may be present. We found significant differences in species diversity and richness between the rainwater and soil populations in grassland areas by analyzing the sample community structures. Our research results revealed the species composition and structure of the microbiota in grassland ecosystems in China, indicating that environmental media and human activities may affect the microbiota in the grassland area and indicating underlying microorganisms with high INA.

Rainwater chemistry in a subtropical high-altitude mountain site, South China: Seasonality, source apportionment and potential factors

Long-term and frequent observation of rainwater chemistry provides an opportunity to explore the evolution of air pollutant emissions and the effectiveness of the emission control measures. This study presents variations in rainwater chemistry, possible sources of air pollutant emissions, and wet deposition fluxes of ionic species in the rainfall samples during 2018–2020 at Mt. Lushan located in South China. Results showed that the annual volume-weighted mean (VWM) pH of rainwater was 5.8. Moreover, the VWM of 87.7% rainwater samples had pH values above 5.6, which indicated that the atmospheric pollution at Mt. Lushan had less effect during the study period. The polytonic nitrate ion (NO3−), the doubly charged positive calcium ion (Ca2+) and the ammonium ion (NH4+) were the dominant ions in rainwater where Ca2+ and NH4+ were the main neutralizing ionic species for rainwater acidity. The highly seasonal variability of ionic concentrations in rainwater was observed among different ionic species, which is closely associated with meteorological conditions and anthropogenic emissions present in the various seasons. Annual wet deposition flux showed an increasing trend during the entire periods. Hence, the wet flux of NO3− (76.3 kg ha−1 yr−1) was three times higher than the annual wet deposition flux of sulfate (SO42−, 21.7 kg ha−1 yr−1), which points to the fact that acid deposition is still a severe environmental issue in the Mt. Lushan region. Positive matrix factorization (PMF) and correlation matrix were used to identify five sources for ionic species, including aging sea salt, fossil fuel combustion, agriculture, dust, and biomass burning. These findings could be helpful in establishing emission control policies to protect and manage pollution control in the eco-environment in South China.

A combination approach using two functionalized magnetic nanoparticles for speciation analysis of inorganic arsenic

Mercapto- and amino-functionalized magnetic nanoparticles, Fe3O4@SiO2@MPTMS (SMNPs-MPTMS) and Fe3O4@SiO2@APTES (SMNPs-APTES), have been applied as magnetic solid-phase extraction (MSPE) sorbents to directly extract arsenite (As(III)) and arsenate (As(V)) respectively, followed by inductively coupled plasma-mass spectrometry (ICP-MS) detection. Various MSPE parameters were optimized including dose of magnetic adsorbent, pH of sample solution, loading and elution conditions of analytes, adsorption capacity and reusability of SMNPs-MPTMS and SMNPs-APTES for As(III) and As(V) respectively. Under the optimized MSPE conditions, this combined scheme possesses excellent selectivity and strong anti-interference ability without any oxidation or reduction prior to capture of these two species. It is found that with a 25-fold enrichment factor, the limits of detection of As(III) and As(V) were 23.5 and 10.5 ng L−1, respectively. To verify the reliability of the proposed protocol, a certified reference material of environmental water was analyzed, and the results for inorganic arsenic species were in close agreement with the certified values. The applicability of the combination strategy for speciation analysis of inorganic arsenic was evaluated in spiked tap, river, lake and rain water samples. Good recoveries of 89%–96% and 90%–102% were achieved for As(III) and As(V), respectively, with the relative standard deviation ranges of 3.2%–8.0% and 2.5%–7.6%. Through the characterization of functionalized magnetic nanoparticles and the optimization of MSPE experiment, it is confirmed that the existence of mercapto and amino groups on SMNPs-MPTMS and SMNPs-APTES sorbents are responsible for the extraction of As(III) and As(V), respectively, via coordination and electrostatic interactions.

Virome in roof-harvested rainwater of a densely urbanized low-income region

Rainwater harvesting has been considered an affordable practice to supplement the conventional sources of water supply for potable and non-potable uses worldwide. This study characterizes the viral community found in roof-harvested rainwater (RHRW) samples obtained under different rain volumes in a densely urbanized low-income region in Rio de Janeiro, Brazil. Three pilot-scale standardized metal-sheet roofs (same catchment area, material age, and slope – 3%) were installed in the study area aiming at obtaining more reliable and representative samples. Fifty-four samples were collected from six rainfall events from January to April 2019 and concentrated by the skimmed-milk flocculation method. Pools of different rainfall volumes were submitted to high throughput sequencing using the shotgun metagenomic approach. Sequencing was performed on NextSeq platform. Genomic analysis of the virus community revealed that most are RNA non-human viruses, including two main families: Dicistroviridae and Iflaviridae, recognized for infecting arthropods. Bacteriophages were also relatively abundant, with a predominance of DNA phages belonging to Microviridae and Siphoviridae families, showing percentages from 5.3 and 3.7% of the total viral hits present in these samples, respectively. Viral genomic RNA viruses (77%) predominated over DNA viruses (23%). Concerning number of viral species identified, a higher percentage was observed for plant viruses (12 families, 58%). Hepatitis A virus and human klassevirus 1 were detected among the established human pathogens, suggesting the need for RHRW treatment before it is considered for human consumption. Australian bat lyssavirus was also detected, emphasizing the importance of environmental monitoring facing emerging viruses. The results corroborate the influence of the surrounding area on the rainwater quality.

Evaluation of Rainwater Quality in Different Areas of Dhaka City

Since rainwater harvesting system was assessed to be potential in residential, industrial, educational and other institutions so the study was focused on the rainwater quality of samples collected from rooftop surface runoff of different locations of Dhaka city which is the 2nd most polluted city of the world. Locations were based upon residential, commercial, industrial zone within the area, motorized vehicles use, population, construction works etc. The rooftops were taken mainly of concrete made rooftops and within a single area 03 locations were chosen and a sample of rainwater was collected from a tin made rooftop within that area. The main purpose of this assessment was to compare the rainwater quality of different locations with the drinking water quality standards of Bangladesh and World Health Organization (WHO) in order to observe whether the water needs of further treatment or not for potable use. The samples were checked of physical (Turbidity) and chemical (pH, Electric Conductivity, Total Dissolved Solids, Nitrate, Nitrite, Sulfate, Chloride & Fluoride) characteristics of water quality. In terms of pH, Nitrate and Fluoride values, there were significant imbalance with the standards and thus required treatment for potable use. And other parameters were within the standards.

Assessment of Rainwater and Groundwater Quality in Izombe Town, Oguta Local Government Area of Imo State

Rainwater and groundwater quality in Izombe were assessed. Five water samples were collected from five (5) different locations, with at least one location from one of the four autonomous communities in Izombe, Oguta L.G.A of Imo State. The physicochemical and microbial parameters of rainwater and groundwater samples from Umuakpa, Ndeuloukwu, Ugbele, Ndioko, and Orsu were assessed using Varian Atomic Absorption Spectrophotometer (AAS). The study was aimed to assess the physicochemical and microbial qualities of groundwater and rainwater in Izombe and how these affect their health as individual members of the community, and their environment when compared to WHO standards. The water samples were collected from five different locations, with at least one location from each of the four autonomous communities, and were assessed. The result indicated that rainwater and groundwater pollutants in the community were turbidities, ammonia, copper and temperatures 7.59±0.02 ph, 6.42±0.28 nitrate, 59.56±0.50 ammonia, 0.29±0.07 phosphate, 0.88±0.03 iron, copper, lead, nickel, aluminum, mercury, manganese, cadmium, bacteria count, coliform count, and E-coli. Also, all the pollutant parameters were identified, only iron, copper, aluminum, and bacteria count were not identified as being associated with petroleum products and exploratory activities. This research has broadened the understanding of the suitability of Izombe water sources for both consumption and other purposes. The findings show that the rain and groundwater sources of the community are not fit for human consumption, due to the contaminants inherent in them, attributed majorly to the oil production activities in the area which corroborates other research studies.

Variation of Groundwater and Rainwater Quality in a Nigerian Leper Colony

Adequate supply of potable water is a major challenge in most leper colony with emphasis often placed on water needs of “normal” people but little concern on the safe water source for the physically challenged and vulnerable lepers with limited mobility who cannot search for other sources of water outside designated colony. This study was designed to investigate the quality of water sources within a Nigerian leper colony. Periodic characterization of groundwater and rainwater samples was conducted using American Public Health Association (APHA) methods to determine physico-chemical parameters; appearance, odour, colour, taste, chloride, pH, sulphate, copper, zinc, iron, nitrate and bacteriological parameters; coliform organism and Escherichia coli (E-coli) against the world health organization (WHO) drinking water standard. Water samples were clear and odourless. Most of the parameters tested from both sources; groundwater and rainwater were within the recommended standard. Results from short term water quality parameters taken from 2010-2012 were relatively within the same range while the long-term decadal water quality parameters showed slight variation compared to the short term. Heavy metals showed remarkable variation in 2019 while bacteriological parameters from both water sources were above the permissible threshold. For potable use, water sources require adequate treatment. Boiling or disinfection is recommended until water samples have been retested to ascertain that contamination has been eliminated. In addition, home water-treatment through the use of filters, solar disinfection, or flocculants should be provided to make the water safe.

Wet Deposition of Mercury and Dissolved Organic Carbon during Pre-Monsoon and Monsoon Periods at Sitapuri Site in Delhi (India)

This rainwater chemistry study was carried out during monsoon and pre-monsoon seasons in 2018. The rainwater samples were collected in the residential area of Sitapuri which is situated the southwest zone of city Delhi. The rainwater samples were collected with the help of the funnel and bottle assembly on event basis. To refrain any contamination from the ground, the assembly was mounted at 5m above the ground level on a terrace. The assembly was always installed on the onset of rain and retrieved soon after the rain stopped. The collected samples were filtered. The samples were analyzed for Mercury (Hg0), Total Nitrogen (TN) and Dissolved Organic Carbon (DOC). The Hg(o) determination was done using Differential Pulse Anodic Stripping Voltammetry through standard addition methods and DOC species and TN species were determined using DOC/TN analyzer (Shimadzu model LCPH/CPN). The average concentration of Hg0 was recorded as 54.9 μg/l, while that of DOC and TN as 160.2 mg/l and 12.6 mg/l respectively. The study indicated that Hg0 and DOC were not contributed by common emission sources. Also, the study indicated that pre-monsoon air was more contaminated with Hg (0), TN and DOC as compared to the monsoon season.

Correlation of Tritium Concentration in Rainwater with Cosmic Rays: Preliminary Results

The Radiochronology Center has been established in 1999 as a member of the Horizontal Laboratories network of the University of Ioannina. Recently it has added to its activities the development of a tritium measurements laboratory as part of the Radiochronology Center. The laboratory is equipped with a super low level background liquid scintillation counter, which is capable to measure very low concentrations of tritium for applications in radioprotection, dating and hydrology.For the aims of the present continuing study rainwater samples are collected monthly. Each sample is distilled and then it is passed through an electrolysis process to increase the tritium concentration. Five mL of the enriched sample are mixed with 15 mL of a scintillation cocktail, specially designed for tritium measurements and its beta activity is measured for 200 min. The LLD of tritium in the samples is estimated 3 Bq/L or 27 TU.Our preliminary results show that, during the measuring period tritium concentration increased with time. The tritium values are correlated with the cosmic ray neutron flux data at ground level, available for Greece in the same period. The measured tritium concentrations in rainwater, which range from 36 ± 8 to 64 ± 8 TU, may be used for local hydrology studies.

A study of the nitrogen and phosphorus imbalance in East Asia based on the distribution patterns of and stoichiometric variation in global atmospheric nitrogen and phosphorus

To explore nitrogen (N) and phosphorus (P) imbalances in the atmosphere in East Asia, we set up an atmospheric sampling station at the southern end of the East China Sea. From April 2019 to March 2020, we collected atmospheric particulates and rainwater samples and performed chemical analyses of inorganic and organic N and P species in the samples. In this study, the average N/P ratio of dry deposition was 443 ± 366, and it was affected mainly by changes in the wind direction in different seasons. The average N/P ratio of wet deposition was 333 ± 362, and the distribution of the ratio was affected mainly by rainfall.In addition, this study categorized the global N and P fluxes into four distribution patterns: high N and high P (HNHP), high N and low P (HNLP), low N and high P (LNHP), and low N and low P (LNLP). The Galloway/Mahowald ratio (G/M ratio) ranges and distribution areas of these four types are 450–2200 (Western Europe, southeastern South America), 660–4400 (East Asia, North America), 0.2–200 (Southern Europe, North Africa) and 45–450 (South Asia). Among them, mainland China in East Asia (HNLP) usually has a higher G/M ratio. The study area has the same characteristics as most HNLP regions (coastal China and the southeastern coast of North America). This study also highlights the imbalance in the ratio of N to P caused by excessive active N emissions from human activities.

The novel Outer Plug Standardization (OPS) calibration strategy applied in a new method for the high-throughput determination of Cl−, NO3− and SO4−2 in rainwater samples

This paper presents the Outer Plug Standardization – OPS, a novel technique as an alternative for the classic internal standardization using multiple injection in capillary zone electrophoresis is proposed herein. This technique was applied in a new method for the determination of chloride, nitrate and sulfate in rainwater samples. After the injection accuracy was tested and proved to be a minor error source (average 1.26% RSD), the OPS was applied and it improved the intra-day and inter-day precision of the analytical method by 32.5% and 24.7%, respectively. Using a capillary with effective length of 23.5 cm the electrophoretic separation of the three inorganic anions could be achieved in <1 min, with detection limits of 0.05, 0.09 and 0.11 mg L−1 for chloride, nitrate and sulfate, respectively. Also, the statistical t-test was applied to the results obtained for 82 rainwater samples that were collected and analyzed applying both the method developed in this study and the official APHA 4140 method where no statistical difference was noted within a 95% confidence level.

Typhoon Control of Precipitation Dual Isotopes in Southern China and Its Palaeoenvironmental Implications

AbstractHigh‐resolution stalagmite oxygen isotope (δ18O) records are widely employed in palaeoclimate studies as indicators of East Asian Monsoon intensity in southern China. A key issue is whether the East Asian Monsoon or other factors control δ18O in precipitation in southern China, which requires modern observations to confirm. To understand which factors control the dual isotopes (δD and δ18O) of precipitation in southern China, δD and δ18O were measured from 412 precipitation events (including 144 rainwater samples from a total of 43 typhoon events) from May 2015 to April 2020 in Zhanjiang, a tropical city frequently affected by typhoon events in southern China. The overall relationship between δD and δ18O can be expressed as δD = 8.961 δ18O + 6.235; significantly lower intercept and larger slope of this relationship compared to these of the global meteoric water line (GMWL) and the China meteoric water line (CMWL). Remarkably, significantly low D‐excess and the lowest δD and δ18O occurred in the typhoon periods, suggesting that typhoon events could bring large amounts of remote moisture to this tropical city from the Western Pacific and South China Sea. The moisture from remote oceans would affect precipitation with the lowest δ18O and D‐excess, which could be responsible for the deviation of the slope and intercept from those of the CMWL and GMWL. Therefore, variations of the δ18O in precipitation are intensively influenced by typhoons, not by the East Asian Monsoon, providing new understanding for the interpretation of palaeo‐isotope data in southern China.

Designing a moderately hydrophobic sol-gel monolithic Carbowax 20 M sorbent for the capsule phase microextraction of triazine herbicides from water samples prior to HPLC analysis

The determination of triazine herbicides in water samples is of utmost importance, due to their persistence and excessive use. However, since the concentration of triazine pesticides in real samples is low, an extraction/preconcentration step is typically required. Capsule phase microextraction (CPME) is a recently introduced sample preparation technique in which highly efficient sol-gel sorbents are encapsulated in a tubular polymer membrane. This particular design integrates the filtration and stirring mechanism into one extraction device, enabling the application of CPME for in situ sampling. In this study, CPME coupled to high performance liquid chromatography-diode array detection (HPLC-DAD) was employed for the first time for the determination of six triazine herbicides (i.e., simazine, cyanazine, atrazine, prometryn, terbuthylazine and propazine) in water samples. Microextraction capsules containing a moderately hydrophobic sol‐gel Carbowax 20 M sorbent provided the highest extraction efficiency towards the examined pesticides. The main parameters affecting the adsorption and desorption steps of the CPME procedure were investigated and optimized. Under the selected conditions, limits of detection (signal/noise = 3.3) were 0.15 ng mL−1 for the target analytes. Moreover, the relative standard deviation for the within-day and between-days repeatability were less than 7.2% and 9.9%, respectively. The method was successfully applied to the analysis of mineral water, tap water, rainwater and lake water samples. The reported protocol could overcome the need for sample filtration prior to the sample preparation of the water samples, resulting in simplification of the overall sample handling, improved data quality with minimal loss of analytes and reduced sample preparation cost.

Multiple isotopic tracing for sulfate and base cation sources of precipitation in Hangzhou city, Southeast China: Insights for rainwater acidification mechanism

Acid deposition has been regarded as a serious factor in the deteriorative water environment and ecosystems. Despite the powerful acid emission control measures have been implemented by the Chinese government, many areas (especially Southeast China) are still suffering from acid deposition. The chemical and isotopic (δ34S and 87Sr/86Sr) compositions of rainwater in Hangzhou, a typical megacity in Southeast China with serious acid rain problem, for one year were studied with the aim to better constrain potential sources and explore the causes of rainwater acidification. Most rainwater samples were acidic, with a VWM pH value of 4.65. SO42− was the dominant anion and the main acid ion in rainwater. Sulfur isotope and the quantity equilibrium model revealed that sea salt, crustal, biogenic, and anthropogenic sulfur represented 2.3%, 0.1%, 16.7%, and 80.8% of the SO42− source in rainwater, respectively. The back trajectory and strontium isotopes indicated that the base cations (BCs) in rainwater originated mainly from anthropogenic sources. The relatively low neutralizing capacity caused by limited BCs input and emission control measures undermines some efforts to reduce rainwater acidity. This case study demonstrated that a valuable tool to probe the source of acid rain and unravel the mechanism of rainwater acidification can be provided by multiple lines of evidence, including rainwater chemical compositions, stable sulfur isotopes, and stable strontium isotopes.

On the performance of carbon-based screen-printed electrodes for (in)organic hydroperoxides sensing in rainwater

Hydroperoxides play important roles in atmospheric chemical processes since they act as strong oxidants. This paper details with the modification, characterization and performance of different carbon-based screen-printed electrodes to develop a sensor that allows to analyze organic and inorganic hydroperoxides in atmospheric samples. Commercial electrodes made up of graphite, graphene, carbon nanotubes and graphene oxide were electrochemically activated and subsequently modified by layer-by-layer method with a conducting polymer of azure-A and electrodeposited platinum nanoparticles. Characterization of modified electrodes was performed by FE-SEM, XPS, Raman spectroscopy, cyclic voltammetry, and impedance spectroscopy. Even though all modified carbonaceous substrates enabled the development of competitive electrochemical sensors for (in)organic hydroperoxides detection, carbon nanotubes underlying substrate exhibited the best performances in terms of sensitivity, stability, limit of detection and linear range. This amperometric sensor displayed linear responses to hydroperoxides over 0.081–450 μM with detection limits in the range of 24–558 nM and sensitivity values among 0.0628±1.6E-4 and 0.0112±0.71E-4 μA/μM for the different hydroperoxides herein studied. The developed electrochemical sensor was successfully applied to the analysis of (in)organic hydroperoxides in rainwater samples. Measurements in rainwater were performed in a city located in the East of Spain and collected at two different sites (downtown and suburban area) on two different dates (July and November 2020). The presented results demonstrated high sensitivity and selectivity for the detection of hydroperoxides among a plethora of substances naturally present in rainwater.

Levels and Compositions of Polycyclic Aromatic Hydrocarbons in Rainwater and Their Implication for Aquatic Environments in Urban Area in Saitama, Japan

In this study, we investigated concentrations and profiles of polycyclic aromatic hydrocarbons (PAHs) in rainwater and surface water samples collected in Saitama, an urban city located in Japan. The volume-weighted mean concentration of total PAHs in rainwater samples (dissolved + particulate) was 108.8 ng L−1 with a range of 17.6–192.9 ng L−1. Two and three benzene ring PAHs were predominantly detected, occupying 67.0% of the total concentration in rainwater samples. Individual PAH concentrations were negatively correlated with their K ow, suggesting that low-molecular-weight PAHs are preferentially scavenged owing to the higher hydrophilicity. The toxic equivalent calculated based on the relative potencies of individual PAHs showed high toxic contributions by chrysene and benz[a]anthracene in the rainwater samples. Those PAHs levels in rainwater were comparable or higher than those in adjacent river water. Correlation coefficient of PAH signatures between rainwater and surface water samples was high particularly in the dissolved phase, supporting the source/sink relationships of PAHs between wet deposition samples and receiving waters. The mean deposition flux of PAHs was 2000 ng m−2 and considered to increase with precipitation amounts.

Assessment of a Photoreactor with Immobilized Nanoparticle TiO2 Films for the Purification of Rainwater

The heterogeneous photocatalysis consists of the generation of reactive oxygen species (•OH, •-O2) from a catalyst, UV light, and oxygen; these reactive species can degrade contaminants and eliminate microorganisms. The purpose of this research was to evaluate a heterogeneous photocatalysis system and an UV light disinfection system for the elimination of total coliforms and Escherichia coli bacteria present in rainwater stored in five cisterns in Mexico City. The elimination of total coliforms (MPN/100 mL) and Escherichia coli (CFU/100 mL) were evaluated both in the rainwater treated with TiO2/UV and UV (in time periods of 30 and 60 minutes), according to the treatments established in the statistical model 22. The results show that although complete elimination of initial total coliforms (9.3 x 104 MPN/100 mL) and E. coli bacterium (1.5 x 103 CFU/mL) was achieved in one of the samples of rainwater using only UV light at 254 nm for 30 minutes, the use of 8 films coated with Degussa P-25 titanium dioxide, UV light at 254 nm and 1.5 vvm air in a reactor, achieves a total pathogen removal in a shorter time of 15 minutes. Thus, we anticipate that the combined treatment could be an alternative disinfection process for rainwater stored in cisterns, reducing costs and making the treatment viable for a larger-scale application.